Make a version of Active Record (“not an extension to ”http://wiki.rubyonrails.com/rails/pages/ActiveRecord" class="existingWikiWord">ActiveRecord":http://sourceforge.net/mailarchive/message.php?msg_id=9182966 ) that runs on a Madeleine back-end. It would obviously not deal with custom SQL, but should be able to handle all the other standard Active Record features. It would require an external DRb server and should be configurable as an adapter.
Since Madeleine wouldn’t have a schema to query for column information, you would need to implement a macro defining the attributes:
class Post < ActiveRecord::Base
attributes :title => :string, :body => :text, :written_on => :datetime
end
This would allow people to start development on Madeleine and later move on to a database-backed engine. Or stay with Madeleine (once their fears of prevaylence have evaporated).
Perhaps while we are at it we should look at the interface between ActionPack and the model in general. See GenericModelDiscussion.